Container (abstract data type)

In computer science, a container is a class, a data structure,[1][2] or an abstract data type (ADT) whose instances are collections of other objects. In other words, they store objects in an organized way that follows specific access rules. The size of the container depends on the number of objects (elements) it contains. Underlying (inherited) implementations of various container types may vary in size and complexity, and provide flexibility in choosing the right implementation for any given scenario.

"Container (computer science)" redirects here. For the abstract notion of containers in type theory, see Container (type theory). For other uses, see Container (disambiguation).

Function and properties

Containers can be characterized by the following three properties:

  • access, that is the way of accessing the objects of the container. In the case of arrays, access is done with the array index. In the case of stacks, access is done according to the LIFO (last in, first out) order and in the case of queues it is done according to the FIFO (first in, first out) order;
  • storage, that is the way of storing the objects of the container;
  • traversal, that is the way of traversing the objects of the container.

Container classes are expected to implement methods to do the following:

  • create an empty container (constructor);
  • insert objects into the container;
  • delete objects from the container;
  • delete all the objects in the container (clear);
  • access the objects in the container;
  • access the number of objects in the container (count).

Containers are sometimes implemented in conjunction with iterators.

Types

Containers may be classified as either single-value containers or associative containers.

Single-value containers store each object independently. Objects may be accessed directly or with an iterator.

An associative container uses an associative array, map, or dictionary, composed of key-value pairs, such that each key appears at most once in the container. The key is used to find the value, the object, if it is stored in the container. Associative containers are used in programming languages as class templates.

Container abstract data types include:

Common data structures used to implement these abstract types include:

Graphic containers

Widget toolkits also use containers, which are special widgets to group other widgets, such as windows, panels. Apart from their graphical properties, they have the same type of behavior as container classes, as they keep a list of their child widgets, and allow adding, removing, or retrieving widgets among their children.

See also

References
  1. Paul E. Black (ed.), entry for data structure in Dictionary of Algorithms and Data Structures. US National Institute of Standards and Technology.15 December 2004. Accessed 4 Oct 2011.
  2. Entry data structure in the Encyclopædia Britannica (2009) Online entry Accessed 4 Oct 2011.
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